1. Field of the Invention
The present invention relates to a camera provided with a zoom lens having a plurality of lens groups.
2. Description of Relevant Art
Conventionally, a compact camera provided with a lens shutter type zoom lens has been used extensively. Many of the commercialized cameras are made thinner and more compact by retracting the zoom lens barrel in a collapsed position beyond a focal length variable region of the zoom lens when a photograph is not taken, so that the top end portion of the lens will not protrude from the camera main body. Most of these types of cameras adopt a focus adjusting method, in which focus adjustment is effected by adjusting a relative positional relation of the lens groups that constitute the zoom lens at their respective zooming positions (focal distance positions). For example, in case of a so-called dual-group zoom lens, the focus adjustment is effected by adjusting the position of the rear lens group with respect to the front lens group.
However, with the above focus adjusting method, the relative position of the rear lens group with respect to the front lens group may be displaced from the position where it is supposed to be, and even a slight displacement can give an enormous adverse effect to the resolution of the lens. For this reason, in order to obtain a satisfactory image, it is necessary to maintain the relative positions of the lens groups accurately. Thus, highly accurate-components and assembly are required, which makes it difficult to manufacture inexpensive cameras.
The present invention is devised to solve the above problems, and therefore, has an object to provide a camera capable of obtaining stable resolution and saving the cost.
In order to fulfill the above object, a first camera of cameras of the present invention is a camera provided with a zoom lens having a plurality of lens groups for forming an image of a subject on a predetermined image forming plane by the zoom lens, characterized by comprising: a first driving source; a second driving source; and a lens driving mechanism for effecting (1) a focusing operation by driving the first driving source while maintaining distances among the plurality of lens groups, and (2) a zooming operation by driving the second driving source while changing the distances among the plurality of lens groups.
With the first camera of the present invention, a picture is taken by effecting the zooming operation by driving the second driving source while changing the distances among the plurality of lens groups, and after a desired magnification is obtained by changing the relative distances among the plurality of lens groups, effecting the focus operation by driving the first driving source while maintaining the distances among the plurality of lens groups. Thus, compared with the prior art, by which the focus adjustment is effected by adjusting the position of the rear lens group with respect to the front lens group, for example, the focusing operation can be effected while maintaining the lens resolution accurately by maintaining the relative positions of these lens groups, thereby making it possible to obtain a picture with stable resolution.
The first camera includes the following embodiment. That is, a camera provided with a zoom lens having a plurality of lens groups for forming an image of a subject on a predetermined image forming plane by the zoom lens, characterized by comprising: a first driving source; a rotatable ring, which is allowed to rotate around an optical axis when driven by the first driving source; a focus cylinder connected to the rotatable ring so as to move linearly in an optical axis direction in association with a rotation of the rotatable ring;
a second driving source;
a rotationally movable cylinder engaged with the focus cylinder in the optical axis direction so as to move in association with a movement of the focus cylinder in the optical axis direction, and provided rotatably around the optical axis with respect to the focus cylinder in a rotating direction so as to rotate when driven by the second driving source; and
a plurality of lens holding frames, each holding their respective lens groups and linked to the rotationally movable cylinder so as to move in the optical axis direction relatively with respect to the rotationally movable cylinder in association with a rotation thereof.
With the camera of the above embodiment, a picture is taken by effecting (1) the zooming operation, wherein each of the plurality of lens groups moves relatively in the optical axis direction in association with a rotation of the rotational movable cylinder by driving the second driving source, and thereby changing the distances among the plurality of lens groups, and (2) the focusing operation while maintaining the distances among the plurality of lens groups in association with a rotation of the rotatable ring that is allowed to rotate around the optical axis when driven by the first driving source. Thus, compared with the prior art, by which the focus adjustment is effected by adjusting the position of the rear lens group with respect to the front lens group, stable resolution can be obtained.
The first camera of the present invention may be arranged in such a manner that the first driving source effects the focusing operation by means of rotational driving, and the focusing operation is effected by driving the first driving source to rotate in a forward direction.
Also, the first camera of the present invention may be arranged in such a manner that the first driving source effects the focusing operation by means of rotational driving, and the focusing operation is effected by driving the first driving source to rotate in an inverse direction.
In this manner, the first camera of the present invention may be arranged so as to effect the focusing operation by means of rotational driving toward the zooming up side or toward the zooming down side.
Further, it is preferable that the focus cylinder retracts the rotationally movable cylinder in a camera main body to a collapsed position where no photograph can be taken.
By arranging the focus cylinder in such a manner so as to retract the rotationally movable cylinder in the camera main body to the collapsed position where no photograph can be taken, the camera can be made thinner and more compact.
Also, in order to fulfill the above object, a second camera of the cameras of the present invention is a camera, characterized by comprising: a zoom lens enclosed therein; and a linking portion for linking a first barrel assembly for varying a focal length by changing a relative positional relation in an optical axis direction among a plurality of lens groups forming the zoom lens to a second barrel assembly for changing a position of the first barrel assembly in the optical axis direction with respect to a shooting focus plane, wherein the second barrel assembly is driven first by using a driving force of a driving source, and thence the driving force from the second barrel assembly is delivered to the first barrel assembly through the linking portion.
The second camera includes the following embodiment. That is, a camera, characterized by comprising: a zoom lens enclosed therein; and a linking portion for linking a first barrel assembly for varying a focal length by changing a relative positional relation in an optical axis direction among a plurality of lens groups forming the zoom lens to a second barrel assembly for changing a position of the first barrel assembly in the optical axis direction with respect to a shooting focus plane, wherein: the second barrel assembly is driven first by using a driving force of a single driving source, and thence the driving force is delivered to the first barrel assembly by driving the second barrel assembly; a driving force non-delivering region where the driving force is not delivered is formed within the linking portion of the first barrel assembly and second barrel assembly; and a focus adjustment is effected while the second barrel assembly alone is driven within the driving force non-delivering region.
With the second camera of the above embodiment, the focus adjustment is effected in the driving force non-delivering region while maintaining the relative positional relation of the plurality of lens groups forming the zoom lens in the optical axis direction. Thus, compared with the prior art, by which the focus adjustment is effected by adjusting the position of the rear lens group with respect to the front lens group, a picture can be obtained while maintaining the lens resolution accurately and stably. Thus, neither highly accurate components nor assembly is necessary, and the cost can be saved. In addition, with the camera of the above embodiment, both the zooming operation and focusing operation can be effected by a single driving source, thereby making the arrangement simpler.
In order to fulfill the above object, the second camera of the present invention also includes the following embodiment. That is, a camera, characterized by comprising: a zoom lens enclosed therein; and a linking portion for linking a first barrel assembly for varying a focal length by changing a relative positional relation in an optical axis direction among a plurality of lens groups forming the zoom lens to a second barrel assembly for changing a position of the first barrel assembly in the optical axis direction with respect to a shooting focus plane, wherein: the second barrel assembly is driven first by using a driving force of a single driving source, and thence the driving force is delivered to the first barrel assembly by driving the second barrel assembly; the camera is provided with a collapsed region, in which both of the first barrel assembly and second barrel assembly are retracted in a camera main body when the camera is not in use, and projected to an outside of the camera main body when the camera is in use; a driving force non-delivering region where the driving force is not delivered is provided within the linking portion; a focus adjustment is effected while the second barrel assembly alone is driven in the driving force non-delivering region; and the driving force non-delivering region is included in the collapsed region.
With the second camera of the above embodiment, the driving force non-delivering region is provided, and the driving force non-delivering region is included in the collapsed region. Hence, the focusing operation is effected while the interval of the plurality of lens group is maintained. Consequently, not only can a picture be obtained while maintaining the lens resolution accurately and stably, but also the camera can be made thinner and more compact.
In the collapsed region, the second camera of the above embodiment may be arranged in such a manner that a driving force of the single driving source in one direction is used to drive the second barrel assembly in a projection direction in the collapsed region, and a driving force of the driving source in another direction is used to effect the focus adjustment.
Also, the second camera of the present invention may be described as follows. That is, the second camera of the present invention is a camera provided with a zoom lens having a plurality of lens groups for forming an image of a subject on a predetermined image forming plane by the zoom lens, characterized by comprising:
a driving source, which is allowed to be driven in either a forward direction or an inverse direction; and
a lens driving mechanism for effecting a zooming operation by driving the driving source in a first direction while changing the distances among the plurality of lens groups, and subsequent to the zooming operation, effecting a focusing operation by driving the driving source in a second direction which is opposite to the first direction while maintaining the distances among the plurality of lens groups.
The second camera of the present invention further includes the following embodiment. That is, a camera provided with a zoom lens having a plurality of lens groups for forming an image of a subject on a predetermined image forming plane by the zoom lens, comprising:
a driving source, which is allowed to be driven in either a forward direction or an inverse direction;
a first rotational movable cylinder, which moves in an optical axis direction while rotating around an optical axis when driven by the driving source;
a second rotational movable cylinder engaged with the first rotationally movable cylinder in the optical axis direction so as to move in association with a movement of the first rotationally movable cylinder in the optical axis direction, the second rotational movable cylinder also engaging with the first rotationally movable cylinder in a rotating direction while securing a clearance so as to rotate around the optical axis in association with a rotation of the first rotationally movable cylinder, when the first rotationally movable cylinder inverts a rotating direction, the second rotationally movable cylinder stopping a rotation thereof regardless of a rotation of the first rotationally movable cylinder until the first rotationally movable cylinder rotates for a predetermined angle of rotation, when the first rotationally movable cylinder has rotated for the predetermined angle of rotation, the second rotationally movable cylinder engaging with the first rotationally movable cylinder so as to rotate again in association with a rotation of the first rotationally movable cylinder; and
a plurality of lens holding frames, each holding their respective lens groups and connected to the second rotationally movable cylinder so as to move in the optical axis direction relatively with respect to the second rotationally movable cylinder in association with a rotation thereof.
It is preferable that the second camera of the above embodiment is arranged in such a manner that a lens barrel including the first rotationally movable cylinder, second rotationally movable cylinder, and the plurality of lens holding frames is allowed to be retracted in a camera main body to a collapsed position where no photograph can be taken.